U.S. patent number 10,288,905 [Application Number 15/539,037] was granted by the patent office on 2019-05-14 for optical article comprising an interference coating with high reflectivity in the ultraviolet region.
This patent grant is currently assigned to ESSILOR INTERNATIONAL. The grantee listed for this patent is ESSILOR INTERNATIONAL (COMPAGNIE-GENERALE D'OPTIQUE). Invention is credited to Nicolas Maitre, Delphine Passard.
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United States Patent |
10,288,905 |
Passard , et al. |
May 14, 2019 |
Optical article comprising an interference coating with high
reflectivity in the ultraviolet region
Abstract
The present invention relates to a transparent ophthalmic lens
comprising a substrate having a main front face and a main rear
face, said main front face being coated with a multilayer
interference coating, preferably an anti-reflection coating,
comprising a stack of at least one layer have a refractive index
greater than 1.6 and at least one layer having a refractive index
less than 1.55, characterized in that: the mean reflection factor
on said main front face coated with said interference coating,
between 350 nm and a wavelength between 380 and 400 nm, preferably
between 350 and 380 nm, weighted by the function W(I), is greater
than or equal to 35% for at least one angle of incidence between
0.degree. and 17.degree.; the light reflection factor at 400 nm on
said main front face coated with said interference coating is less
than or equal to 35% for at least one angle of incidence between
0.degree. and 17.degree..
Inventors: |
Passard; Delphine
(Charenton-le-Pont, FR), Maitre; Nicolas
(Charenton-le-Pont, FR) |
Applicant: |
Name |
City |
State |
Country |
Type |
ESSILOR INTERNATIONAL (COMPAGNIE-GENERALE D'OPTIQUE) |
Charenton-le-Pont |
N/A |
FR |
|
|
Assignee: |
ESSILOR INTERNATIONAL
(Charenton-le-Pont, FR)
|
Family
ID: |
53872088 |
Appl.
No.: |
15/539,037 |
Filed: |
December 18, 2015 |
PCT
Filed: |
December 18, 2015 |
PCT No.: |
PCT/FR2015/053656 |
371(c)(1),(2),(4) Date: |
June 22, 2017 |
PCT
Pub. No.: |
WO2016/102857 |
PCT
Pub. Date: |
June 30, 2016 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20170351119 A1 |
Dec 7, 2017 |
|
Foreign Application Priority Data
|
|
|
|
|
Dec 24, 2014 [FR] |
|
|
14 63344 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B
5/283 (20130101); G02B 1/116 (20130101); G02B
5/26 (20130101); G02B 1/115 (20130101); G02C
7/104 (20130101); G02C 7/107 (20130101) |
Current International
Class: |
G02C
7/10 (20060101); G02B 1/115 (20150101); G02B
1/116 (20150101); G02B 5/26 (20060101); G02B
5/28 (20060101) |
Field of
Search: |
;351/159.48,159.49,159.62,159.6,159.65 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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|
|
|
|
0404111 |
|
Dec 1990 |
|
EP |
|
0614957 |
|
Sep 1994 |
|
EP |
|
0680492 |
|
Apr 1997 |
|
EP |
|
0933377 |
|
Aug 1999 |
|
EP |
|
1085348 |
|
Mar 2001 |
|
EP |
|
2607884 |
|
Jun 2013 |
|
EP |
|
2702486 |
|
Sep 1994 |
|
FR |
|
2990774 |
|
Nov 2013 |
|
FR |
|
S6387223 |
|
Apr 1988 |
|
JP |
|
S63141001 |
|
Jun 1988 |
|
JP |
|
H01230003 |
|
Sep 1989 |
|
JP |
|
WO 2013/171435 |
|
Nov 2013 |
|
WO |
|
WO 2014/057226 |
|
Apr 2014 |
|
WO |
|
Other References
Citek et al., "Anti-Reflective coatings reflect ultraviolet
radiation", Optometry--Journal of the American Optometric
Association, vol. 19, No. 3, (2008), pp. 143-148. cited by
applicant.
|
Primary Examiner: Collins; Darryl J
Attorney, Agent or Firm: Norton Rose Fulbright US LLP
Claims
The invention claimed is:
1. A transparent ophthalmic lens comprising a substrate having a
front main face and a back main face, said front main face being
coated with a multilayer interference coating comprising a stack of
at least one layer having a refractive index higher than 1.6,
called the high-refractive-index layer, and of at least one layer
having a refractive index lower than 1.55, called the
low-refractive-index layer, and which does not contain titanium,
wherein: the average reflectance of said coated front main face of
said interference coating, between 350 nm and a wavelength
comprised between 380 and 400 nm, weighted by the function
W(.lamda.), is higher than or equal to 50% at at least one angle of
incidence comprised between 0.degree. and 17.degree.; and the light
reflectance at 400 nm of said coated front main face of said
interference coating is lower than or equal to 35% at at least one
angle of incidence comprised between 0.degree. and 17.degree..
2. The ophthalmic lens of claim 1, wherein said multilayer
interference coating is an antireflection coating.
3. The ophthalmic lens of claim 1, wherein the average reflectance
of said coated front main face of said interference coating,
between 350 nm and a wavelength comprised between 350 and 380 nm,
weighted by the function W(.lamda.), is higher than or equal to 50%
at at least one angle of incidence comprised between 0.degree. and
17.degree..
4. The ophthalmic lens of claim 1, wherein said average reflectance
of said front main face between 350 nm and a wavelength comprised
between 380 and 400 nm is higher than or equal to 65% at at least
one angle of incidence comprised between 0.degree. and
17.degree..
5. The ophthalmic lens of claim 1, wherein the light reflectance at
400 nm of said coated front main face of said interference coating
is lower than or equal to 25% at at least one angle of incidence
comprised between 0.degree. and 17.degree..
6. The ophthalmic lens of claim 5, wherein the light reflectance at
400 nm of said coated front main face of said interference coating
is lower than or equal to 15% at at least one angle of incidence
comprised between 0.degree. and 17.degree..
7. The ophthalmic lens of claim 1, wherein said multilayer
interference coating comprises a number of layers higher than or
equal to 3 and a number of layers lower than or equal to 10.
8. The ophthalmic lens of claim 7, wherein said multilayer
interference coating comprises a number of layers higher than or
equal to 4 and a number of layers lower than or equal to 8.
9. The ophthalmic lens of claim 8, wherein said multilayer
interference coating comprises a number of layers higher than or
equal to 6 and a number of layers lower than or equal to 8.
10. The ophthalmic lens of claim 1, wherein the one or more
high-refractive-index layers of the multilayer interference coating
have a refractive index higher than or equal to 1.8.
11. The ophthalmic lens of claim 10, wherein the one or more
high-refractive-index layers of the multilayer interference coating
have a refractive index higher than or equal to 1.9.
12. The ophthalmic lens of claim 1, wherein the light reflected
from said coated front main face of said interference coating has a
chroma C* lower than or equal to 15 at at least one angle of
incidence comprised between 0.degree. and 17.degree..
13. The ophthalmic lens of claim 12, wherein the light reflected
from said coated front main face of said interference coating has a
chroma C* lower than or equal to 10 at at least one angle of
incidence comprised between 0.degree. and 17.degree..
14. The ophthalmic lens of claim 1, wherein the substrate has a
transmittance T higher than or equal to 1% at a wavelength located
between 350 nm and 400 nm.
15. The ophthalmic lens of claim 1, wherein the reflectance in the
visible Rv between 380 nm and 780 nm of said coated front main face
of said interference coating is lower than or equal to 3%.
16. The ophthalmic lens of claim 15, wherein the reflectance in the
visible Rv between 380 nm and 780 nm of said coated front main face
of said interference coating is lower than or equal to 1.5%.
17. The ophthalmic lens of claim 1, wherein the interference
coating comprises, in order starting from the substrate: a
high-refractive-index layer having a refractive index higher than
1.6 of 15 to 39 nm thickness; a low-refractive-index layer having a
refractive index lower than 1.55 of 26 to 62 nm thickness; a
high-refractive-index layer having a refractive index higher than
1.6 of 24 to 63 nm thickness; a low-refractive-index layer having a
refractive index lower than 1.55 of 52 to 81 nm thickness; a
high-refractive-index layer having a refractive index higher than
1.6 of 24 to 45 nm thickness; a low-refractive-index layer having a
refractive index lower than 1.55 of 27 to 64 nm thickness; a
high-refractive-index layer having a refractive index higher than
1.6 of 28 to 58 nm thickness; a low-refractive-index layer having a
refractive index lower than 1.55 of 84 to 116 nm thickness.
18. The ophthalmic lens of claim 17, wherein the interference
coating comprises, in order starting from the substrate: a
high-refractive-index layer having a refractive index higher than
1.6 of 15 to 35 nm thickness; a low-refractive-index layer having a
refractive index lower than 1.55 of 42 to 62 nm thickness; a
high-refractive-index layer having a refractive index higher than
1.6 of 24 to 44 nm thickness; a low-refractive-index layer having a
refractive index lower than 1.55 of 61 to 81 nm thickness; a
high-refractive-index layer having a refractive index higher than
1.6 of 25 to 45 nm thickness; a low-refractive-index layer having a
refractive index lower than 1.55 of 27 to 57 nm thickness; a
high-refractive-index layer having a refractive index higher than
1.6 of 30 to 58 nm thickness; a low-refractive-index layer having a
refractive index lower than 1.55 of 84 to 114 nm thickness.
19. The ophthalmic lens of claim 18, wherein the interference
coating further comprises an electrically conductive layer of 3 to
10 nm thickness between the a high-refractive-index layer having a
refractive index higher than 1.6 of 30 to 58 nm thickness and the
low-refractive-index layer having a refractive index lower than
1.55 of 84 to 114 nm thickness.
20. The ophthalmic lens of claim 17, wherein the interference
coating comprises, in order starting from the substrate: a
high-refractive-index layer having a refractive index higher than
1.6 of 19 to 39 nm thickness; a low-refractive-index layer having a
refractive index lower than 1.55 of 26 to 46 nm thickness; a
high-refractive-index layer having a refractive index higher than
1.6 of 43 to 63 nm thickness; a low-refractive-index layer having a
refractive index lower than 1.55 of 52 to 72 nm thickness; a
high-refractive-index layer having a refractive index higher than
1.6 of 24 to 44 nm thickness; a low-refractive-index layer having a
refractive index lower than 1.55 of 44 to 64 nm thickness; a
high-refractive-index layer having a refractive index higher than
1.6 of 28 to 48 nm thickness; a low-refractive-index layer having a
refractive index lower than 1.55 of 95 to 116 nm thickness.
21. The ophthalmic lens of claim 20, wherein the interference
coating further comprises an electrically conductive layer of 3 to
10 nm thickness between the high-refractive-index layer having a
refractive index higher than 1.6 of 28 to 48 nm thickness and the
low-refractive-index layer having a refractive index lower than
1.55 of 95 to 116 nm thickness.
22. The ophthalmic lens of claim 17, wherein the interference
coating further comprises an electrically conductive layer of 3 to
10 nm thickness between the high-refractive-index layer having a
refractive index higher than 1.6 of 28 to 58 nm thickness and the
low-refractive-index layer having a refractive index lower than
1.55 of 84 to 116 nm thickness.
23. The ophthalmic lens of claim 1, wherein the reflectance in the
UV R.sub.uv, of said back main face between 280 nm and 380 nm,
weighted by the function W(.lamda.), is lower than or equal to 10%
at an angle of incidence of 35.degree..
24. The ophthalmic lens of claim 23, wherein the reflectance in the
UV R.sub.uv, of said back main face between 280 nm and 380 nm,
weighted by the function W(.lamda.), is lower than or equal to 5%
at an angle of incidence of 35.degree..
25. The ophthalmic lens of claim 1, wherein the ESPF coefficient of
the lens is higher than 10.
26. A process for manufacturing an ophthalmic lens of claim 1,
wherein the multilayer interference coating is vacuum deposited.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a national phase application under 35 U.S.C.
.sctn. 371 of International Application No. PCT/FR2015/053656 filed
18 Dec. 2015, which claims priority to French Patent Application
No. 1463344 filed 24 Dec. 2014. The entire contents of each of the
above-referenced disclosures is specifically incorporated by
reference herein without disclaimer.
TECHNICAL FIELD OF THE INVENTION
The present invention generally relates to an article, in
particular a transparent optical article, such as an ophthalmic
lens, comprising an interference stack allowing the transmission of
ultraviolet light through an ophthalmic lens to be decreased.
PRIOR ART
The solar spectrum is composed of electromagnetic radiation of
various wavelengths and in particular of ultraviolet (UV) rays. The
UV spectrum includes a number of bands, in particular the UVA, UVB
and UVC bands. Among the UV bands that reach the surface of the
Earth, the UVA band, comprised between 315 nm and 380 nm, and the
UVB band, comprised between 280 nm and 315 nm, are particularly
harmful to the eye. These bands are in particular responsible for
accelerated ocular aging, which can lead to early cataracts or even
to more extreme phenomena such as photokeratitis or "snow
blindness". The UV protection level of an ophthalmic lens is
considered to be inadequate when the ophthalmic lens lets pass more
than 1% of wavelengths between 280 nm and 380 nm.
However, certain of the materials commonly used as ophthalmic lens
substrates, for example the materials obtained by
(co)polymerization of di(ethylene glycol) bis(allyl carbonate)
(such materials for example being sold under the trade name
CR-39.RTM. by the company PPG Industries (ESSILOR ORMA.RTM.
lenses)) let some of the ultraviolet light between 350 nm to 380 nm
pass. Specifically, it has been observed that this type of
substrate lets pass some of the UV in this wavelength range.
Therefore, these materials do not provide perfect protection from
the harmful ultraviolet light between 280 and 380 nm. This leads to
two major problems: firstly ophthalmic lenses made from these
materials have a low ESPF (acronym of "Eye-Sun Protection Factor",
such as defined in European patent application EP2607884) of about
10/15, and secondly substrates made from these materials yellow
over time due to degradation caused by this UV.
Conventional antireflection coatings are designed and optimized to
decrease reflection at the surface of the glass in the visible
domain, typically in the spectral range extending from 380 to 780
nm. In general, reflection in the UV domain (280-380 nm) is not
optimized.
In order to prevent the ocular damage caused by these UV rays and
obtain a lens having a UV cut-off (the longest wavelength at which
the lens blocks at least 99% of the UV light) higher than or equal
to 365 nm and generally equal to 380 nm, various solutions have
been proposed in the prior art.
A first solution consists in decreasing reflection in the UV
spectrum by coating the back face of a lens substrate with a
multilayer antireflection coating.
Document FR 2968774 for example describes a lens substrate
comprising on its back face a multilayer antireflection coating.
This multilayer antireflection coating has an average reflectance
Ruv between 280 and 380 nm, weighted by the function W(.lamda.)
defined in standard ISO 13666:1998, lower than 5%, at an angle of
incidence of 30.degree. and at an angle of incidence of
45.degree..
For example, example 1 of this document discloses use of an
antireflection coating comprising, starting from the substrate, a
stack of 4 layers of high (ZrO.sub.2) to low (SiO.sub.2) refractive
index. The reflectance in the UV of this example at an angle of
incidence of 35.degree. is: R.sub.UV.sup.35.degree.(%)=4%. The
coating tested in this example furthermore allows, depending on the
tested substrate, an ESPF ranging from 11 to 25 to be obtained, as
table 1 below shows:
TABLE-US-00001 TABLE 1 The ESPF value of the stack of example 1
depending on the substrate Substrate Orma .RTM. 15 Orma .RTM. thin
PC MR7 .RTM. MR8 .RTM. T.sub.UV.sup.0.degree.(%) 3.87% 5.26% 0 0 0
ESPF-value 13 11 25 25 25 and class Class 10 Class 10 Class 25
Class 25 Class 25
Thus, this table shows that ESPF value was lower with Orma.RTM.
lenses based on di(ethylene glycol) bis(allyl carbonate) than with
other substrates, this confirming that Orma.RTM. substrates
transmit UV of between 350 nm and 380 nm. The Orma Thin.RTM.
substrate, which has a smaller center thickness and which therefore
lets even more harmful UV rays pass, had an even lower ESPF
value.
Therefore, depending on the substrate, the ESPF of the ophthalmic
lens described in document FR 2968774 is unsatisfactory.
Another solution allowing a UV-blocking ophthalmic lens to be
obtained is to decrease transmission in the UV
(T.sub.UV.sup.0.degree.(%)), for example by integrating UV
absorbers into the ophthalmic lens.
The UV absorber may be incorporated into the bulk of the lens,
during the polymerization of the monomers forming the material of
the lens, or be placed on the surface of the latter, by dipping the
lens into (or imbibing the lens in) a bath containing the UV
absorber.
Incorporation of a UV absorber into a lens is generally accompanied
by an undesirable yellowing of the latter, which may be overcome by
combining the UV absorber with a specific dye.
Patent application EP 1 085 348 discloses a process for
incorporating a UV absorber into a lens without yellowing the
latter. This process consists in mixing a benzotriazole-based UV
absorber with a di(ethylene glycol) bis(allyl carbonate) or
episulfide monomer, which is subsequently polymerized in order to
form the material of the lens. The use of this specific UV absorber
in this particular process allows long-wavelength UV radiation to
be absorbed.
In addition, there has been suggested, in patent application
JP01-230003, a process for imbibing a lens using another
benzotriazole derivative,
2-(2-hydroxy-5-methylphenyl)benzotriazole.
However, although these solutions using UV absorbers are
satisfactory, they implement a quite complex process.
Another known prior-art solution allowing transmission
T.sub.UV.sup.0.degree.(%) to be decreased consists in coating the
substrate with an antireflection stack that rejects ultraviolet
rays.
Document U.S. Pat. No. 5,332,618 for example describes a
UV-rejecting multilayer antireflection coating able to be deposited
on a transparent (mineral glass) substrate. This coating comprises
at least eight layers. It is formed by an alternation, from the
substrate, of high-refractive-index layers (refractive index higher
than or equal to 2.10 at a wavelength of 520 nm) and of
low-reflective-index layers (refractive index of less than 1.50 at
a wavelength of 520 nm). In particular, a set of five successive
layers, each of the layers being 1/4 of a wavelength thick, is
flanked by two low-refractive-index layers that are each 1/8 of a
wavelength thick, at a wavelength of 330 nm. It is indicated that
the reflection of the UV is improved by the constraints on the
thickness of these two low-refractive-index layers.
Example 3 of this document illustrates a coating comprising an
alternation of eight layers of high-refractive index (made of
TiO.sub.2) and of low-refractive-index layers (made of SiO.sub.2).
The optical article according to this example, which has been
reproduced by the Applicant, has a reflectance at 400 nm of 46% at
an angle of incidence of 0.degree. and a reflectance in the UV of
86% for a wavelength range extending from 350 to 380 nm. Therefore,
the coating according to this example has the effect of blocking
visible light in the blue, leading to an undesirable yellowing of
the optical article.
This document furthermore discloses that a high-refractive-index
layer made of zirconia (ZrO.sub.2) is not recommended because it
would lead to less effective and/or more complex coatings.
Therefore, although these solutions are satisfactory, there is
still a need for new optical articles, such as ophthalmic lenses,
that, while providing a very good antireflection performance in the
visible domain, have improved anti-UV properties and are simple to
produce.
Moreover, polycarbonate-based substrates filter at least 99% of
light of wavelengths shorter than 385 nm, whereas substrates made
of poly(thiourethane)s filter at least 99% of light of wavelength
shorter than 395-398 nm. In this violet range of visible light from
380 nm to 400 nm, it may also be advantageous to limit transmission
through ophthalmic lenses.
Thus, the aim of the present invention is to provide a new optical
article, in particular an ophthalmic article, that avoids all or
some of the aforementioned drawbacks.
In particular, the objective of the present invention is to provide
a transparent optical article, in particular an ophthalmic lens,
that comprises a substrate made of mineral or organic glass
including, on its front face, an anti-UV, and preferably
antireflection, multilayer interference coating providing a very
good antireflection performance in the visible domain and capable,
at the same time, of significantly decreasing, relative to a bare
substrate or a substrate including a conventional antireflection
coating, the transmission of UV rays, and in particular of UVA and
UVB rays, and that it is easy to produce industrially.
SUMMARY OF THE INVENTION
The present invention relates to a transparent ophthalmic lens
comprising a substrate having a front main face and a back main
face, said front main face being coated with a, preferably
antireflection, multilayer interference coating comprising a stack
of at least one layer having a refractive index higher than 1.6,
called the high-refractive-index layer, and of at least one layer
having a refractive index lower than 1.55, called the
low-refractive-index layer, characterized in that: the average
reflectance of said coated front main face of said interference
coating, between 350 nm and a wavelength comprised between 380 and
400 nm and preferably between 350 and 380 nm, weighted by the
function W(.lamda.), is higher than or equal to 35% at at least one
angle of incidence comprised between 0.degree. and 17.degree.; and
the light reflectance at 400 nm of said coated front main face of
said interference coating is lower than or equal to 35% at at least
one angle of incidence comprised between 0.degree. and
17.degree..
In the context of the invention, the angle of incidence is defined
in the conventional way as the angle between the normal to the
surface at the point of incidence and the direction of the light
beam striking said surface.
The present invention also relates to a process for manufacturing
an ophthalmic lens such as defined above, characterized in that the
multilayer interference coating is vacuum deposited.
In the rest of the description, unless otherwise specified, the
indication of a range of values "from X to Y" or "between X and Y"
will be understood, in the present invention, as including the
values X and Y.
In the present patent application, when an optical article (or
ophthalmic lens) comprises one or more coatings on its surface, the
expression "to deposit a layer or a coating on the article" means
that a layer or a coating is deposited on the uncovered (exposed)
surface of the external coating of the article, that is to say the
coating furthest from the substrate.
A coating that is "on" a substrate or that has been deposited "on"
a substrate is defined as a coating that (i) is positioned above
the substrate, (ii) does not necessarily make contact with the
substrate, i.e. one or more intermediate coatings may be arranged
between the substrate and the coating in question, and (iii) does
not necessarily completely cover the substrate.
In one preferred embodiment, the coating on a substrate or
deposited on a substrate makes direct contact with said
substrate.
When "a layer 1 is located under a layer 2", it will be understood
that the layer 2 is further from the substrate than the layer
1.
By back (or internal) face of the substrate, what is meant is the
face which, when the optical article (or ophthalmic lens) is being
used, is closest to the eye of the user. This is generally a
concave face. In contrast, by front face of the substrate, what is
meant is the face which, when the optical article (or ophthalmic
lens) is being used, is furthest from the eye of the user. This is
generally a convex face.
DESCRIPTION OF THE FIGURES
The invention will be described in more detail with reference to
the following appended drawings, in which:
FIG. 1 and FIG. 2 show graphs illustrating the variation in the
reflectance R in percent (R %) of optical articles (lens 1 and lens
3, respectively) that are according to the invention, prepared
according to example 1 and example 3, respectively, and that each
comprise an antireflection coating on their front main face, at an
angle of incidence .theta. of 0.degree. and as a function of
wavelength (lambda) in the UVA (315 to 380 nm), UVB (280 to 315 nm)
and visible (380 to 780 nm) domains.
DETAILED DESCRIPTION OF THE INVENTION
The Applicant has sought to develop a new ophthalmic lens
comprising a new, preferably antireflection, multilayer
interference stack, the front (convex) face of which has a high
reflectance measured at an angle of incidence close to normal, in
the ultraviolet domain.
The Applicant has shown that the new multilayer interference stack
according to the invention allows, surprisingly, the amount of UV
passing through substrates, and in particular Orma.RTM. substrates,
to be decreased, without however reflecting visible light and
without causing yellowing of the lens.
The Applicant has also shown that the new multilayer interference
stack according to the invention allows ESPF to be greatly
increased, without however increasing reflectance in the
visible.
Lastly, the method for producing this new anti-UV multilayer
interference stack is easy to implement. In particular, it is
easier to implement than the UV absorbers that must be incorporated
into the substrate. In addition, the required materials are the
same as those required for standard antireflection coatings.
Thus, the present invention relates to a transparent ophthalmic
lens comprising a substrate having a front main face and a back
main face, said front main face being coated with a, preferably
antireflection, multilayer interference coating comprising a stack
of at least one layer having a refractive index higher than 1.6,
called the high-refractive-index layer, and of at least one layer
having a refractive index lower than 1.55, called the
low-refractive-index layer, characterized in that: the average
reflectance of said coated front main face of said interference
coating, between 350 nm and a wavelength comprised between 380 and
400 nm and preferably between 350 and 380 nm, weighted by the
function W(.lamda.), is higher than or equal to 35% at at least one
angle of incidence comprised between 0.degree. and 17.degree.; and
the light reflectance at 400 nm of said coated front main face of
said interference coating is lower than or equal to 35% at at least
one angle of incidence comprised between 0.degree. and
17.degree..
Specifically, the present invention proposes an anti-UV multilayer
interference coating with an improved design, including a stack of
thin layers the thicknesses and materials of which have been chosen
so as to optimize the antireflection performance in the visible
domain on the one hand and in the UV domain on the other.
This optimization of antireflection performance was achieved by
taking into account the weighting function W(.lamda.) defined in
standard ISO 13666:1998, which expresses the distribution of UV
solar radiation weighted by the wearer's spectral sensitivity to
this radiation. In the wavelength range from 280 nm to 380 nm, the
average reflectance corresponds to the factor Ruv well known to
those skilled in the art.
In order to take account of violet visible light in the 380 nm to
400 nm range, the weighting function W(.lamda.) has been
extrapolated to 400 nm, defining an analogue to Ruv extended to
violet and ultraviolet light.
Unexpectedly, the inventors have developed an anti-UV multilayer
interference coating having a high reflectance in the UV, leading
to a decrease in UV transmission, the first consequence of which is
to allow ESPF to be increased. A second consequence of this
decrease in the amount of UV transmitted to the substrate is that
the latter is "protected" and therefore its degradation and
consequently the increase in its yellow index over time is
limited.
The multilayer interference coatings according to the invention
therefore have, without affecting the wearer, a higher spectral
reflectance between 280 and 380 nm, in order to achieve the best
compromise between antireflection performance in the visible domain
and in the UV domain
Generally, the multilayer interference coating of the ophthalmic
lens according to the invention, which will be referred to as the
"UV-reflecting interference coating", may be deposited on any
substrate, but will preferably be deposited on substrates made of
organic glass, for example of thermoplastic or thermoset.
Regarding thermoplastics suitable for the substrates, mention may
be made of (meth)acrylic (co)polymers, in particular polymethyl
methacrylate (PMMA), thio(meth)acrylic (co)polymers, polyvinyl
butyral (PVB), polycarbonates (PC), polyesters such as polyethylene
terephthalate (PET) or polybutylene terephthalate (PBT),
polycarbonate/polyester copolymers, cyclic olefin copolymers such
as ethylene/norbornene or ethylene/cyclopentadiene copolymers and
their blends, and vinyl acetate/ethylene thermoplastic
copolymers.
Regarding thermosets suitable for the substrates, mention may be
made of the polyurethanes (PU), the poly(thiourethane)s,
polyol(allyl carbonate) (co)polymers, the polyepisulfides, and the
polyepoxides.
Other thermosets suitable for the substrates are acrylic
(co)polymers the refractive index of which is comprised between 1.5
and 1.65 and typically close to 1.6. These acrylic (co)polymers are
obtained by polymerization of blends of (meth)acrylate monomers and
optionally aromatic vinyl and/or allyl monomers.
These (meth)acrylate monomers may be monofunctional or
multifunctional and typically bear 2 to 6 (meth)acrylate groups.
These monomers may be aliphatic, cyclic, aromatic, polyalkoxylated,
derivatives of compounds such as bisphenol and/or bearing other
functions such as epoxy, thioepoxy, hydroxyl, thiol, sulfide,
carbonate, urethane and/or isocyanate functions.
The term "(co)polymer" is understood to mean a copolymer or a
polymer. The term "(meth)acrylate" is understood to mean an
acrylate or a methacrylate. The term "polycarbonate (PC)" is
understood in the context of the present invention to mean both
homopolycarbonates and copolycarbonates and sequenced
copolycarbonates. The substrates may be obtained by polymerization
of blends of the above monomers, or may even comprise blends of
these polymers and (co)polymers.
Preferably, the substrate according to the invention has a
transmittance T higher than or equal to 1% at a wavelength located
between 350 nm and 400 nm.
Substrates obtained by (co)polymerization of the di(ethylene
glycol) bis(allyl carbonate) sold, for example, under the trade
name CR-39.RTM. by PPG Industries (ESSILOR ORMA.RTM. lenses), or
acrylic substrates are particularly recommended.
In particular, the substrate recommended for the invention is the
substrate obtained by (co-)polymerization of di(ethylene glycol)
bis(allyl carbonate) (CR-39.RTM. ESSILOR ORMA.RTM. lenses).
Before the UV-reflecting interference coating is deposited on the
substrate, which is optionally coated, for example with an
anti-abrasion and/or anti-scratch layer or an underlayer, it is
common to subject the surface of said optionally coated substrate
to a physical or chemical activation treatment intended to increase
the adhesion of the UV-reflecting interference coating. This
pre-treatment is generally carried out under vacuum. It may be a
question of a bombardment with energetic species, for example an
ion beam (ion pre-cleaning or IPC), a corona discharge treatment, a
glow discharge treatment, a UV treatment or treatment in a vacuum
plasma, generally an oxygen or argon plasma. It may also be a
question of an acidic or basic surface treatment and/or a treatment
with solvents (water or organic solvent(s)).
In the present invention, the average light reflectance, denoted
Rv, is such as defined in standard ISO 13666:1998, and is measured
according to standard ISO 8980-4 (at an angle of incidence smaller
than 17.degree., typically 15.degree.), i.e. it is a question of
the weighted average of the spectral reflectance over all of the
visible spectrum between 380 nm and 780 nm. Preferably, the
reflectance in the visible Rv between 380 nm and 780 nm of said
coated front main face of said UV-reflecting interference coating
is lower than or equal to 3% and preferably lower than or equal to
1.5%.
Preferably, the light reflectance at 400 nm of said coated front
main face of said UV-reflecting interference coating is lower than
or equal to 25% and preferably lower than or equal to 15% at at
least one angle of incidence comprised between 0.degree. and
17.degree..
According to the invention, the average reflectance between 280 and
380 nm, weighted by the function W(.lamda.) defined in standard ISO
13666:1998 and denoted Ruv, is defined by:
.intg..times..function..lamda..function..lamda..times..times..lamda..intg-
..times..function..lamda..times..times..lamda. ##EQU00001##
where R(.lamda.) designates the spectral reflectance of the glass
at the wavelength in question, and W(.lamda.) designates a
weighting function equal to the product of the solar spectral
irradiance Es(.lamda.) and the relative spectral sensitivity
function S(.lamda.) (referred to as the relative spectral
effectiveness function in standard ISO 13666:1998).
By analogy, the average reflectance weighted by the function
W(.lamda.) may be defined between two wavelengths .lamda.1 and
.lamda.2 if the equation above is rewritten and the limits of the
integral set equal to the wavelengths .lamda.1 and .lamda.2.
The spectral function W(.lamda.), which allows average
transmittances to be calculated for UV rays, is defined in standard
ISO 13666:1998. It allows the distribution of solar UV rays
moderated by the relative spectral sensitivity of a wearer to this
radiation to be expressed, since it takes into account both the
spectral energy of the sun Es(.lamda.), which on the whole emits
little UVB with respect to the UVA, and the spectral sensitivity
S(.lamda.), the UVB being more harmful than the UVA. This function
has in the context of the invention been extrapolated to violet
visible light of 385 to 400 nm. The values of these three functions
in the UV domain are indicated in table 2 below (the bold texted
cells are extrapolated)
TABLE-US-00002 TABLE 2 Es(.lamda.) (mW/m.sup.2 nm) S(.lamda.)
W(.lamda.) = Es(.lamda.) S(.lamda.) 280 0 0.88 0 285 0 0.77 0 290 0
0.64 0 295 2.09 .times. 10.sup.-4 0.54 0.00011 300 8.10 .times.
10.sup.-2 0.30 0.0243 305 1.91 0.060 0.115 310 11.0 0.015 0.165 315
30.0 0.003 0.09 320 54.0 0.0010 0.054 325 79.2 0.00050 0.04 330 101
0.00041 0.041 335 128 0.00034 0.044 340 151 0.00028 0.042 345 170
0.00024 0.041 350 188 0.00020 0.038 355 210 0.00016 0.034 360 233
0.00013 0.03 365 253 0.00011 0.028 370 279 0.000093 0.026 375 306
0.000077 0.024 380 336 0.000064 0.022 385 0.02 390 0.018 395 0.016
400 0.014
It should be noted that the weighting function W(.lamda.) is zero
or almost zero between 280 nm and 295 nm, this meaning that the
weighted average reflectance is also zero in this wavelength range.
This means that even if the reflectance level is high in this
spectral range, it will have no effect on the value of the weighted
average reflectance Ruv calculated between 280 and 380 nm
According to the invention, the UV-reflecting interference coating
deposited on the front main face of the substrate preferably has an
average reflectance from said front main face between 350 nm and a
wavelength comprised between 380 and 400 nm, weighted by the
function W(.lamda.), higher than or equal to 50% and preferably
higher than or equal to 65% at at least one angle of incidence
comprised between 0.degree. and 17.degree..
According to one feature of the invention, the color coordinates of
the UV-reflecting interference coating of the invention in the CIE
L*a*b* color space are calculated between 380 and 780 nm using
illuminant D65 and a 10.degree. observer.
The UV-reflecting interference coatings produced are not limited
with regard to their hue angle. However, the hue angle h preferably
ranges from 90.degree. to 180.degree. and preferably from
120.degree. to 150.degree., this producing a coating having a green
reflection, and the chroma C* is in general lower than or equal to
15 and better still lower than or equal to 10 at at least one angle
of incidence comprised between 0.degree. and 17.degree..
The, preferably antireflection, UV-reflecting interference coating
of the invention comprises a stack of at least one
high-refractive-index layer and at least one low-refractive-index
layer. Better still, it comprises at least two layers of low
refractive index (LI) and at least two layers of high refractive
index (HI). It is a question of a simple stack, because the total
number of layers of the UV-reflecting interference coating is
higher than or equal to 3 and preferably higher than or equal to
4.
In particular, the UV-reflecting interference coating of the
invention comprises a number of layers higher than or equal to 3,
preferably higher than or equal to 4 and ideally higher than or
equal to 6, and a number of layers lower than or equal to 10 and
preferably lower than or equal to 8.
A layer of the UV-reflecting interference coating is defined as
having a thickness larger than or equal to 1 nm. Thus, any layer
having a thickness smaller than 1 nm will not be counted in the
number of layers of the UV-reflecting interference coating.
Unless otherwise indicated, all the thicknesses disclosed in the
present patent application are physical thicknesses.
It is not necessary for the HI and LI layers to alternate in the
stack, although they can be alternating according to one embodiment
of the invention. Two (or more) HI layers can be deposited on one
another, just as two (or more) LI layers can be deposited on one
another.
In the present patent application, a layer of the, preferably
antireflection, UV-reflecting interference coating is said to be a
high-refractive-index (HI) layer when its refractive index is
higher than 1.6, preferably higher than or equal to 1.65, more
preferably higher than or equal to 1.7, even more preferably higher
than or equal to 1.8 and even better still higher than or equal to
1.9. A layer of the, preferably antireflection, UV-reflecting
interference coating is said to be a low-refractive-index (LI)
layer when its refractive index is lower than 1.55, preferably
lower than or equal to 1.48 and better still lower than or equal to
1.47.
Unless otherwise indicated, the refractive indices to which
reference is made in the present application are expressed at
25.degree. C. for a wavelength of 550 nm.
The HI layers are conventional high-refractive-index layers, well
known in the art. They generally contain one or more mineral oxides
such as, nonlimitingly, zirconia (ZrO.sub.2), titanium oxide
(TiO.sub.2), alumina (Al.sub.2O.sub.3), tantalum pentoxide
(Ta.sub.2O.sub.5), neodymium oxide (Nd.sub.2O.sub.5), praseodymium
oxide (Pr.sub.2O.sub.3), praseodymium titanate (PrTiO.sub.3),
La.sub.2O.sub.3i, Nb.sub.2O.sub.5i, or Y.sub.2O.sub.3. Optionally
the high-index layers may also contain silica or other
low-refractive-index materials, provided that their refractive
index is higher than 1.6 as indicated above. Preferred materials
are TiO.sub.2, PrTiO.sub.3, ZrO.sub.2, Ta.sub.2O.sub.5,
Al.sub.2O.sub.3, Y.sub.2O.sub.3 and their mixtures.
Preferably, the one or more HI layers are made of zirconia
(ZrO.sub.2).
The LI layers are also well-known low-refractive-index layers and
may comprise, nonlimitingly: silicon oxide, or else a mixture of
silica and alumina, in particular silica doped with alumina, the
latter contributing to increase the thermal resistance of the
UV-reflecting interference coating. Each LI layer is preferably a
layer comprising at least 80% by weight silica and better still at
least 90% by weight silica, relative to the total weight of the
layer, and even better still consists of a silica layer.
Optionally, the low-index layers may also contain
high-refractive-index materials, provided that the refractive index
of the resulting layer is lower than 1.55.
When a LI layer comprising a mixture of SiO.sub.2 and
Al.sub.2O.sub.3 is used, it preferably comprises from 1% to 10% by
weight, better still from 1% to 8% by weight and even better still
from 1% to 5% by weight of Al.sub.2O.sub.3, with respect to the
total weight of SiO.sub.2+Al.sub.2O.sub.3 in this layer.
For example, SiO.sub.2 doped with 4% or less Al.sub.2O.sub.3 by
weight, or SiO.sub.2 doped with 8% Al.sub.2O.sub.3 may be employed.
Commercially available SiO.sub.2/Al.sub.2O.sub.3 mixtures may be
used, such as the LIMA.RTM. mixture sold by Umicore Materials AG
(refractive index comprised between n=1.48-1.50 to 550 nm) or the
substance L5.RTM. sold by Merck KGaA (refractive index n=1.48 to
500 nm).
The external layer of the UV-reflecting antireflection coating is
in general a layer based on silica, preferably comprising at least
80% by weight silica and better still at least 90% by weight silica
(for example a layer of silica doped with alumina) relative to the
total weight of the layer, and even better still consists of a
silica layer.
Generally, the HI layers have a physical thickness ranging from 10
nm to 120 nm and the LI layers have a physical thickness ranging
from 10 nm to 100 nm.
Generally, the total thickness of the UV-reflecting interference
coating is smaller than 1 micrometer, preferably smaller than or
equal to 800 nm, better still smaller than or equal to 500 nm and
even better still smaller than or equal to 250 nm. The total
thickness of the UV-reflecting interference coating is generally
greater than 100 nm, preferably greater than 150 nm.
According to one preferred embodiment, the UV-reflecting
interference coating according to the invention does not contain
titanium.
According to one embodiment of the invention, the, preferably
antireflection, UV-reflecting interference coating is deposited on
an underlayer. This underlayer is considered not to form part of
the UV-reflecting interference coating.
The expression "underlayer of the UV-reflecting interference
coating" is understood to mean a coating of relatively large
thickness used with the aim of improving mechanical properties such
as the resistance of said coating to abrasion and/or scratches
and/or to promote its adhesion to the substrate or to the subjacent
coating.
On account of its relatively large thickness, the underlayer
generally does not participate in the antireflective optical
activity, in particular in the case where it possesses a refractive
index similar to that of the underlying coating (which is generally
an anti-abrasion and anti-scratch coating) or that of the substrate
when the underlayer is deposited directly on the substrate.
Therefore, the underlayer, when it is present, is not considered to
form part of the UV-reflecting interference coating.
The underlayer must be thick enough to increase the resistance of
the UV-reflecting interference coating to abrasion, but preferably
not too thick in order not to absorb light as, depending on the
nature of the underlayer, this could significantly decrease the
relative transmittance .tau..sub.v. Its thickness is generally
smaller than 300 nm and better still 200 nm and is generally larger
than 90 nm and better still 100 nm.
The underlayer preferably comprises a layer based on SiO.sub.2,
this layer preferably comprising at least 80% by weight silica and
better still at least 90% by weight silica relative to the total
weight of the layer, and even better still this layer consists of a
silica layer. The thickness of this silica-based layer is generally
smaller than 300 nm and better still 200 nm and is generally larger
than 90 nm and better still 100 nm.
According to another embodiment, this SiO.sub.2-based layer is a
layer of silica doped with alumina, in proportions such as defined
above, and preferably consists of a layer of silica doped with
alumina.
According to one particular embodiment, the underlayer consists of
a layer of SiO.sub.2.
It is preferable for the underlayer to be a monolayer. However, the
underlayer may be laminated (multilayer), in particular when the
underlayer and the underlying coating (or the substrate if the
underlayer is deposited directly on the substrate) have a
non-negligible refractive index difference.
The ophthalmic lens of the invention may be made antistatic, i.e.
such as to not retain and/or develop an appreciable electrostatic
charge, by virtue of the incorporation of at least one electrically
conductive layer into the stack present on the surface of the
ophthalmic lens. This electrically conductive layer is preferably
located between two layers of the UV-reflecting interference
coating and/or is adjacent to a high-refractive-index layer of this
UV-reflecting interference coating. Preferably, the electrically
conductive layer is located immediately under a
low-refractive-index layer of the UV-reflecting interference
coating, and ideally forms the penultimate layer of the
UV-reflecting interference coating, i.e. it is located immediately
under the silica-based external layer of the UV-reflecting
interference coating.
The electrically conductive layer must be sufficiently thin not to
decrease the transparency of the UV-reflecting interference
coating. The electrically conductive layer is preferably made from
an electrically conductive and highly transparent material,
generally an optionally doped metal oxide. In this case, its
thickness preferably ranges from 1 to 15 nm and more preferably
from 1 to 10 nm. The electrically conductive layer preferably
comprises an optionally doped metal oxide chosen from indium oxide,
tin oxide, zinc oxide and their mixtures. Indium tin oxide
(tin-doped indium oxide, In.sub.2O.sub.3:Sn), aluminum-doped zinc
oxide (ZnO:Al), indium oxide (In.sub.2O.sub.3), and tin oxide
(SnO.sub.2) are preferred. According to one optimal embodiment, the
electrically conductive and optically transparent layer is a layer
of indium tin oxide (ITO) or a layer of tin oxide.
Generally, the electrically conductive layer contributes, within
the stack, but to a limited extent, because of its small thickness,
to the obtainment of antireflection properties and forms a
high-refractive-index layer in the UV-reflecting interference
coating. This is the case for layers made from an electrically
conductive and highly transparent material such as layers of
ITO.
The various layers of the UV-reflecting interference coating and
the optional underlayer are preferably deposited by vacuum
deposition using one of the following techniques: i) by evaporation
and optionally ion-beam-assisted evaporation ii) by ion-beam
sputtering iii) by cathode sputtering iv) by plasma-enhanced
chemical vapor deposition.
These various techniques are described in the works "Thin Film
Processes" and "Thin Film Processes II", edited by Vossen and Kern,
Academic Press, 1978 and 1991, respectively. A particularly
recommended technique is the vacuum evaporation technique.
Preferably, each of the layers of the UV-reflecting interference
coating and the optional underlayer are deposited by vacuum
evaporation.
According to one embodiment of the invention, the anti-UV
interference coating comprises, in order starting from the
substrate, which is optionally coated with one or more functional
coatings and an underlayer of 100 to 200 nm thickness, which is
preferably made of silica, a high-refractive-index layer having a
refractive index higher than 1.6 of 15 to 39 nm thickness, a
low-refractive-index layer having a refractive index lower than
1.55 of 26 to 62 nm thickness, a high-refractive-index layer having
a refractive index higher than 1.6 of 24 to 63 nm thickness, a
low-refractive-index layer having a refractive index lower than
1.55 of 52 to 81 nm thickness, a high-refractive-index layer having
a refractive index higher than 1.6 of 24 to 45 nm thickness, a
low-refractive-index layer having a refractive index lower than
1.55 of 27 to 64 nm thickness, a high-refractive-index layer having
a refractive index higher than 1.6 of 28 to 58 nm thickness,
optionally an electrically conductive layer of 3 to 10 nm
thickness, and a low-refractive-index layer having a refractive
index lower than 1.55 of 84 to 116 nm thickness.
According to another embodiment, the UV-reflecting interference
coating comprises, in order starting from the substrate, which is
optionally coated with one or more functional coatings and an
underlayer of 100 to 200 nm thickness, which is preferably made of
silica, a high-refractive-index layer having a refractive index
higher than 1.6 of 15 to 35 nm thickness, a low-refractive-index
layer having a refractive index lower than 1.55 of 42 to 62 nm
thickness, a high-refractive-index layer having a refractive index
higher than 1.6 of 24 to 44 nm thickness, a low-refractive-index
layer having a refractive index lower than 1.55 of 61 to 81 nm
thickness, a high-refractive-index layer having a refractive index
higher than 1.6 of 25 to 45 nm thickness, a low-refractive-index
layer having a refractive index lower than 1.55 of 27 to 57 nm
thickness, a high-refractive-index layer having a refractive index
higher than 1.6 of 30 to 58 nm thickness, optionally an
electrically conductive layer of 3 to 10 nm thickness, and a
low-refractive-index layer having a refractive index lower than
1.55 of 84 to 114 nm thickness.
According to another embodiment, the UV-reflecting interference
coating comprises, in order starting from the substrate, which is
optionally coated with one or more functional coatings and an
underlayer of 100 to 200 nm thickness, which is preferably made of
silica, a high-refractive-index layer having a refractive index
higher than 1.6 of 19 to 39 nm thickness, a low-refractive-index
layer having a refractive index lower than 1.55 of 26 to 46 nm
thickness, a high-refractive-index layer having a refractive index
higher than 1.6 of 43 to 63 nm thickness, a low-refractive-index
layer having a refractive index lower than 1.55 of 52 to 72 nm
thickness, a high-refractive-index layer having a refractive index
higher than 1.6 of 24 to 44 nm thickness, a low-refractive-index
layer having a refractive index lower than 1.55 of 44 to 64 nm
thickness, a high-refractive-index layer having a refractive index
higher than 1.6 of 28 to 48 nm thickness, optionally an
electrically conductive layer of 3 to 10 nm thickness, and a
low-refractive-index layer having a refractive index lower than
1.55 of 95 to 116 nm thickness.
According to one preferred embodiment of the invention, the back
face of the ophthalmic lens of the invention is also coated with a
conventional antireflection coating that is different from that
located on its front face, intended to limit the reflection of UV
originating from the sides and/or behind the lens.
Thus, according to one preferred embodiment, the back face of the
ophthalmic lens is coated with an antireflection coating such that
the reflectance in the UV R.sub.uv of said back main face between
280 nm and 380 nm, weighted by the function W(.lamda.), is lower
than or equal to 10%, preferably lower than or equal to 5% and
ideally lower than or equal to 3%, at an angle of incidence of
35.degree..
In the context of the invention, the ESPF of an ophthalmic lens is
given by the following relationship:
.times..times..degree..function..times..degree..function.
##EQU00002## where T.sub.UV.sup.0.degree.(%) is the amount of UV
(between 280 and 380 nm) transmitted at an angle of incidence of
0.degree. (i.e. the UV source is perpendicular to the lens), and
R.sub.UV.sup.35.degree.(%) is the amount of UV (between 280 nm and
380 nm) reflected at an angle of incidence of 35.degree. from the
back face.
The ESPF values calculated according to the formula below are
illustrated in the following table, for back-face Ruv values lower
than 5%, for various front-face Ruv values and for the material
ORMA.RTM.:
TABLE-US-00003 TABLE 3 ESPF Ruv@35.degree. back (1-Ruv)@0.degree.
front face on ORMA .RTM. side 1 0.65 0.5 0.35 0.2 0 0.05 11.27
13.31 14.42 15.74 17.32 20.00 0.04 12.71 15.35 16.85 18.68 20.95
25.00 0.03 14.56 18.13 20.26 22.96 26.50 33.33 0.02 17.04 22.15
25.41 29.81 36.05 50.00 0.01 20.53 28.45 34.07 42.47 56.37
100.00
The cells with italic text correspond to an ESPF of 15 to 20 and
the cells with bold text correspond to an ESPF higher than 20.
Thus, the ophthalmic lens comprising the UV-reflecting interference
coating according to the invention and an antireflection coating
for the UV (i.e. a coating such as mentioned above) on its back
face has an excellent ESPF index.
Preferably, the ESPF coefficient of the ophthalmic lens according
to the invention is higher than 10, preferably higher than 15 and
ideally higher than 20.
It is however possible to apply a UV-reflecting interference
coating such as described in the present application to the back
face of the ophthalmic lens. The UV-reflecting multilayer
interference coatings of the front face and the back face may then
be identical or different.
According to one embodiment of the invention, the back face of the
ophthalmic lens is not coated with a UV-reflecting multilayer
interference coating according to the invention.
The UV-reflecting interference coating may be deposited directly on
a bare substrate.
In some applications, it is preferable for the main face of the
substrate to be coated with one or more functional coatings prior
to the deposition of the UV-reflecting interference coating of the
invention.
These functional coatings, which are conventionally used in optics,
may, nonlimitingly, be: an anti-shock primer layer, an
anti-abrasion and/or anti-scratch coating, a polarized coating, a
photochromic coating or a tinted coating.
Preferably, the ophthalmic lens comprises no photochromic coating
and/or comprises no photochromic substrate.
Generally, the front main face of the substrate i.e. the face on
which a UV-reflecting interference coating will be deposited, is
coated with an anti-shock primer layer, with an anti-abrasion
and/or anti-scratch coating, or with an anti-shock primer layer
coated with an anti-abrasion and/or anti-scratch coating.
The UV-reflecting interference coating of the invention is
preferably deposited on an anti-abrasion and/or anti-scratch
coating. The anti-abrasion and/or anti-scratch coating may be any
layer conventionally used as an anti-abrasion and/or anti-scratch
coating in the field of ophthalmic lenses.
The abrasion-resistant and/or to scratch-resistant coatings are
preferably hard coatings based on poly(meth)acrylates or on silanes
generally comprising one or more mineral fillers intended to
increase the hardness and/or the refractive index of the coating
once cured.
Hard anti-abrasion and/or anti-scratch coatings are preferably
prepared from compositions comprising at least one alkoxysilane
and/or a hydrolyzate of the latter, for example obtained by
hydrolysis with a hydrochloric acid solution and optionally
condensation and/or curing catalysts.
Mention may be made, among the coatings recommended in the present
invention, of coatings based on epoxysilane hydrolyzates, such as
those described in the patents FR 2702486 (EP 0614957), U.S. Pat.
Nos. 4,211,823 and 5,015,523.
A preferred composition for an anti-abrasion and/or anti-scratch
coating is that disclosed in the patent FR 2 702 486 on behalf of
the applicant. It comprises an epoxytrialkoxysilane and
dialkyldialkoxysilane hydrolyzate, colloidal silica and a catalytic
amount of aluminum-based curing catalyst, such as aluminum
acetylacetonate, the remainder being essentially composed of
solvents conventionally used for the formulation of such
compositions. Preferably, the hydrolyzate used is a hydrolyzate of
y-glycidoxypropyltrimethoxysilane (GLYMO) and
dimethyldiethoxysilane (DMDES).
The anti-abrasion and/or anti-scratch coating composition may be
deposited on the main face of the substrate by dip coating or spin
coating. It is subsequently cured by the appropriate route
(preferably thermal or UV).
The thickness of the anti-abrasion and/or anti-scratch coating
generally varies from 2 to 10 .mu.m, preferably from 3 to 5
.mu.m.
It is possible, prior to the deposition of the anti-abrasion and/or
anti-scratch coating, to deposit, on the substrate, a primer
coating which improves the impact resistance and/or the adhesion of
the subsequent layers in the final product. This coating can be any
impact-resistant primer layer conventionally used for articles made
of transparent polymeric material, such as ophthalmic lenses.
Mention may be made, among preferred primer compositions, of
compositions based on thermoplastic polyurethanes, such as those
described in the Japanese patents JP 63-141001 and JP 63-87223,
poly(meth)acrylic primer compositions, such as those described in
the patent U.S. Pat. No. 5,015,523, compositions based on
thermosetting polyurethanes, such as those described in the patent
EP 0 404 111, and compositions based on poly(meth)acrylic latexes
or on latexes of polyurethane type, such as those described in the
patents U.S. Pat. No. 5,316,791 and EP 0 680 492.
Preferred primer compositions are polyurethane-based compositions
and latex-based compositions, in particular polyurethane latexes
optionally containing polyester units.
Among commercially available primer compositions suitable for the
invention, mention may be made of the following: Witcobond.RTM.
232, Witcobond.RTM. 234, Witcobond.RTM. 240, Witcobond.RTM. 242,
Neorez.RTM. R-962, Neorez.RTM. R-972, Neorez.RTM. R-986 and
Neorez.RTM. R-9603.
It is also possible to use in the primer compositions blends of
these latexes, in particular of polyurethane latex and
poly(meth)acrylic latex.
These primer compositions may be deposited on the faces of the
article by dip coating or spin coating then dried at a temperature
of at least 70.degree. C. and possibly of as a high as 100.degree.
C. and preferably of about 90.degree. C., for a time of 2 minutes
to 2 hours and generally of about 15 minutes, in order to form
primer layers having thicknesses, post-bake, of 0.2 to 2.5 .mu.m
and preferably from 0.5 to 1.5 .mu.m.
The ophthalmic lens according to the invention may also comprise
coatings, formed on the UV-reflecting interference coating and
capable of modifying its surface properties, such as hydrophobic
coatings and/or oleophobic coatings (anti-smudge top coat). These
coatings are preferably deposited on the external layer of the
UV-reflecting interference coating. They are generally less than or
equal to 10 nm in thickness, preferably from 1 to 10 nm in
thickness and better still from 1 to 5 nm in thickness.
It is generally a question of fluorosilane or fluorosilazane
coatings. They may be obtained by depositing a fluorosilane or
fluorosilazane precursor preferably comprising at least two
hydrolysable groups per molecule. The fluorosilane precursors
preferably contain fluoropolyether groups and better still
perfluoropolyether groups. These fluorosilanes are well known and
are described, inter alia in U.S. Pat. Nos. 5,081,192, 5,763,061,
6,183,872, 5,739,639, 5,922,787, 6,337,235, 6,277,485 and EP
0933377.
One preferred hydrophobic and/or oleophobic coating composition is
sold by Shin-Etsu Chemical under the denomination KP 801 M.RTM..
Another preferred hydrophobic and/or oleophobic coating composition
is sold by Daikin Industries under the denomination OPTOOL
DSX.RTM.. It is a question of a fluororesin comprising
perfluoropropylene groups.
Typically, an ophthalmic lens according to the invention comprises
a substrate coated in succession on its front face with an
anti-shock primer layer, with an anti-abrasion and/or anti-scratch
layer, with an anti-UV multilayer interference coating according to
the invention, and with a hydrophobic and/or oleophobic coating.
The ophthalmic lens according to the invention is preferably an
ophthalmic lens for a pair of spectacles (spectacle lenses), or an
ophthalmic lens blank. The lens may be a polarized lens, a
photochromic lens, or a tinted sunglass lens, optionally providing
a correction.
The back face of the ophthalmic lens substrate may be coated in
succession with an anti-shock primer layer, with an anti-abrasion
and/or anti-scratch layer, with an antireflection coating that may
or may not be an anti-UV multilayer interference coating according
to the invention, and with a hydrophobic and/or oleophobic
coating.
According to one embodiment, the ophthalmic lens according to the
invention does not absorb in the visible or absorbs little in the
visible, this meaning, in the context of the present application,
that its transmittance .tau..sub.v in the visible (also called
relative transmittance in the visible) is higher than 90%, better
still higher than 95%, even better still higher than 96% and
optimally higher than 97%. The transmittance TV respects a
standardized international definition (standard ISO 13666:1998) and
is measured according to standard ISO 8980-3. It is defined in the
wavelength range extending from 380 to 780 nm.
Preferably, the light absorption of the coated ophthalmic lens
according to the invention is lower than or equal to 1%.
Furthermore, the ophthalmic lens according to the invention is
advantageously used as a component of a pair of spectacles. Thus,
the invention also provides a pair of spectacles comprising at
least one ophthalmic lens according to the invention.
Lastly, the present invention relates to a process for
manufacturing an ophthalmic lens such as described above,
characterized in that the UV-reflecting interference coating is
vacuum deposited.
In particular, the UV-reflecting interference coating is vacuum
deposited using one of the following techniques:
i) by evaporation and optionally ion-beam-assisted evaporation
ii) by ion-beam sputtering
iii) by cathode sputtering
iv) by plasma-enhanced chemical vapor deposition.
These various techniques are described in the works "Thin Film
Processes" and "Thin Film Processes II", edited by Vossen and Kern,
Academic Press, 1978 and 1991, respectively. A particularly
recommended technique is the vacuum evaporation technique.
EXAMPLES
1. General Procedures
The ophthalmic lenses employed in the examples comprise an ESSILOR
ORMA.RTM. lens substrate 30 of 65 mm diameter, of refractive index
of 1.50, of -2.00 diopter power and of 1.2 mm thickness, coated on
its back face with the anti-abrasion and anti-scratch coating (hard
coat) disclosed in example 3 of patent EP 0614957 (of refractive
index equal to 1.47 and of 3.5 .mu.m thickness), based on a
hydrolyzate of GLYMO and DMDES, colloidal silica and aluminum
acetylacetonate, then an antireflection multilayer interference
coating according to the invention.
Said anti-abrasion and anti-scratch coating was obtained by
deposition and curing of a composition comprising, by weight, 224
parts of GLYMO, 80.5 parts of 0.1N HCl, 120 parts of DMDES, 718
parts of 30% by weight colloidal silica in methanol, 15 parts
aluminum acetylacetonate and 44 parts of ethyl cellosolve. The
composition also comprises 0.1% of FLUORAD.TM. FC-430.RTM.
surfactant from 3M, by weight relative to the total weight of the
composition.
The layers of the antireflection coating were deposited without
heating of the substrates by vacuum evaporation (evaporation
source: the electron gun).
The deposition tool was a Satis 1200DLF machine equipped with a
Temescal (8 kV) electron gun for the evaporation of the oxides, and
a (Veeco Mark II) ion gun for the preliminary phase of preparing
the surface of the substrate with argon ions (IPC).
The thickness of the layers was controlled by means of a quartz
microbalance. The spectral measurements were carried out using a
variable-incidence Perkin-Elmer lambda 850 spectrophotometer with a
universal reflectance accessory (URA).
2. Procedure
The process used to prepare the ophthalmic lenses comprised
introducing the substrate coated on its front face with the
anti-abrasion and anti-scratch coating into a vacuum deposition
chamber, a step of pumping the chamber down until a secondary
vacuum was obtained, a step of activating the surface of the
substrate with a beam of argon ions, stopping the ionic
irradiation, forming the underlayer and then the various layers of
the antireflection coating on the anti-abrasion and anti-scratch
coating by successive evaporations and lastly a venting step.
3. Tested Compositions
The structural characteristics and the optical properties of
ophthalmic lenses 1 to 3 obtained according to examples 1 to 3 are
detailed below. The underlayer has been shown in bold, italic text.
The thin ITO layer provides the lens with an antistatic
functionality. Its optical index is close to that of ZrO.sub.2. The
ITO layer and the ZrO.sub.2 layer are therefore considered to form
one high-refractive-index layer.
The values of the average reflectances in the UV and in the visible
are those of the front face and are indicated for an angle of
incidence of 0.degree. (measurements carried out according to
standard ISO8980-4).
TABLE-US-00004 TABLE 4 Lens 1 Lens 2 Lens 3 Example 1 Example 2
Example 3 Refractive (physical (physical (physical index thickness)
thickness) thickness) Air 1 SiO.sub.2 1.47256 94 nm 105 nm 106 nm
ITO 2.0592 6.5 nm 6.5 nm 6.5 nm ZrO.sub.2 1.997 48 nm 38 nm 38 nm
SiO.sub.2 1.47256 37 nm 54 nm 51 nm ZrO.sub.2 1.997 35 nm 34 nm 35
nm SiO.sub.2 1.47256 71 nm 62 nm 69 nm ZrO.sub.2 1.997 34 nm 53 nm
37 nm SiO.sub.2 1.47256 52 nm 36 nm 53 nm ZrO.sub.2 1.997 25 nm 29
nm 19 nm Substrate 2 mm Properties C* 9 9 9 h 145 135 135 Rv 0.70%
0.88% 0.85% Average reflectance 65.4% 67.7% 69.5% [280 nm-380 nm]
Average reflectance 43% 62% 57% [350 nm-380 nm] Average reflectance
35% 53% 48% [350 nm-400 nm] Tuv* [280 nm-380 1.34% 1.25% 1.18% nm]
*Tuv = Tuv(bare Orma)(1 - Ruv) = 3.87% (1 - Ruv)
Graphs of the reflectance between 280 and 780 nm of certain of the
prepared articles (lens 1 and lens 3) have been shown in FIGS. 1
and 2 for an angle of incidence of 0.degree..
4. Results:
It may be seen that ophthalmic lenses 1 to 3 possess very good
antireflection properties in the visible domain (Rv<0.88%) while
decreasing transmission in the UV (Tuv<1.34%) and while having
an excellent average reflectance in the UV: higher than 65% in the
domain [280 nm-380 nm] and in particular higher than 57% in the
domain extending from 350 nm to 380 nm, which is the most
problematic for the substrate Orma.RTM..
The lenses of examples 1 to 3 furthermore have excellent properties
as regards transparency, a good abrasion and scratch resistance and
a good resistance to being dipped in hot water followed by a
mechanical surface solicitation. The adherence of the coatings to
the substrate is also very satisfactory.
5. Comparative Trials
TABLE-US-00005 TABLE 5 Average Average Average reflectance
reflectance reflectance Reflectance [280 nm- [350 nm- [350 nm- at
400 nm Rv 380 nm] 380 nm] 400 nm] Ex 3 of 46.4% 0.40% 57% 86% 81%
US5332618 Example 1 2.3% 0.70% 65.4% 43% 35% Example 2 14.5% 0.88%
67.7% 62% 53% Example 3 12.5% 0.85% 69.5% 57% 48%
As may be seen, ophthalmic lenses according to the invention allow
substantial reflection of UV rays (here, at normal incidence), in
particular in the problematic range of 350 to 380 nm (lenses 2 and
3), while having a low light reflectance at 400 nm.
6. SPF Values of the Lens
The lenses obtained according to examples 1 to 3 may be coated, on
their back face, with an antireflection coating of Ruv between 280
and 380 nm lower than 5% at an angle of incidence of 35.degree..
With the coating of example 1 of patent FR2968774, the ESPF values
are higher than 20 (table 6):
TABLE-US-00006 TABLE 6 Tuv@0.degree. on ORMA Ruv@35.degree. (Tuv =
3.87%(1-Ruv)) back face ESPF Example 1 1.34% 3% 23 Example 2 1.25%
3% 23.5 Example 3 1.18% 3% 24
Although the invention has been described with regard to a
plurality of particular embodiments, it is of course obvious that
it is in no way limited thereto and that it comprises all
techniques equivalent to the means described and their combinations
if these are encompassed within the scope of the invention.
* * * * *